This has taken me a while to solve, so I have decided to share the solution to the problem.
I have created a guest installation of the Windows XP Pro on the Intel based Mac OS 10.5 Leopard. I have used the latest version of the VMWARE FUSION
to create the Windows VM in OS X.
Everything would work just fine in the XP Pro, except the Cisco VPN Client (ver 4.7). The client would connect and establish the tunnel, but I was not able to ping anything on the remote network.
The solution was to setup the networking settings of the Virtual Machine to use the "bridged mode". I have made the change and restarted the Windows XP VM. Apparently, the bridged mode gives the Windows XP a direct access to the networking interface. Sure enough, that was it. The VPN client was now able to send and receive the info from the remote network.